I started 5 years ago, and most of the numbers in datasheets are baffling to me also. The easiest part is the package, because it’s a pic. Like the 328P has a TQFP package with legs, and a 32 MLF with pads, and they usually have an engineering drawing at the bottom for the copper pad footprint to use for each.
I’m doing some tutorials on how to use the FZ advanced features right now, and have some part making ones at the top, if you’re interested.